Experimental study on characteristic stress and acoustic emission characteristics of granite under continued high temperature
In underground engineering such as geological disposal of nuclear waste and geothermal development,the continued high temperature effect leads to a significant reduction in the strength and deformation properties of rocks,inducing engineering disasters.Therefore,it is great significance to investigate the characteristic stress and acoustic emission characteristics of granite under continued high temperature.Uniaxial compression acoustic emission(AE)tests were conducted on granite after different high temperature duration with 350 ℃ and 950 ℃ as the target temperatures.The influence of high temperature duration on characteristic stress points and acoustic emission characteristics was analyzed.The results show that:(1)The granite mass loss rate,volume expansion rate,and P-wave velocity decay rate increase exponentially with increasing high temperature duration.(2)The uniaxial compressive strength,elastic modulus,peak strain and characteristic stress increase exponentially with the increase high temperature duration at 350 ℃.The uniaxial compressive strength,elastic modulus and characteristic stress decrease exponentially with the increase of high temperature duration at 950 ℃ and peak strain opposite.(3)The sensitivity of the characteristic stress under high temperature duration is different,ie.closure stress＞cracking stress＞damage stress＞peak stress.(4)Under 350 ℃ continued high temperature,with the increase of high temperature duration,the AE main frequency of the characteristic stress decreases,the amplitude of AE increases,the multifractal parameters increase,and the small-scale fracture is gradually dominant.Under 950 ℃ continued high temperature,with the increase of high temperature duration,the AE main frequency of the characteristic stress decreases,the amplitude of AE decreases,the multifractal parameters decrease,and the large-scale fracture is gradually dominant.(5)The variations of thermal induced cracks and pores caused by high temperature mainly occur before the duration of 8 h,and after exceeding 8 hours,the impact of high temperature duration on them is significantly reduced.
rock mechanicshigh temperature durationcharacteristic stressacoustic emission(AE)multifractalSEM
NETL
NSTL
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